When carbon is burned in air, the dominant gaseous product of the combustion reaction is carbon dioxide. However, low levels of carbon monoxide are almost always present in the product gases. Because carbon monoxide exhibits adverse health effects, it is desirable to minimize its concentration in combustion products.
The need to reduce carbon monoxide levels during the combustion of a carbonaceous fuel has become a priority in light of recently introduced "smokeless" cigarettes. Such articles are described in U.S. Pat. No. 4,756,318, which issued on July 12, 1988, and U.S. Pat. No. 4,732,168, which issued on Mar. 22, 1988. These patents teach a smoking article which is capable of producing substantial quantities of aerosol, both initially and over the useful life of the product without significant thermal degradation of the aerosol former.
The smoking article is generally taught to comprise a short, combustible, carbonaceous fuel element and, optionally, a separate tobacco jacket around a portion of the aerosol generating means. This combination is taught to present the user with the taste, feel and aroma associated with smoking conventional cigarettes while not requiring the burning of tobacco.
It is taught in the above-referenced patents that the fuel element should comprise carbonaceous materials which can be derived from virtually any of the numerous carbon sources currently known. It is taught that preferably the carbonaceous material is obtained by the pyrolysis or carbonization of cellulosic materials, such as wood, cotton, rayon, tobacco, coconut, paper and the like, although carbonaceous materials from other sources can also be used. It is further taught that the carbonaceous fuel element should be capable of being ignited by a conventional cigarette lighter. These burning characteristics are taught to be obtainable from cellulosic material which has been pyrolyzed at temperatures between about 400.degree. C. to about 1000.degree. C. in an inert atmosphere or under vacuum.
Such carbonaceous fuel elements are also taught to optionally contain such diverse components as oxidizing agents to render the fuel element ignitable by a cigarette lighter, glow retardants or other type or combustion modifying agents such as sodium chloride to improve smoldering and tobacco extracts for flavor. These elements are generally formed as a pressed or extruded mass of carbon prepared from a powdered carbon and binder by conventional press forming or extrusion techniques. Unfortunately, regardless of the heretofore additives employed or physical confirmation of the carbonaceous fuel element, relatively high levels of carbon monoxide, generally at least about 10 milligrams is the product of burning carbonaceous fuel elements in the "smokeless" cigarettes made the subject of the above-referenced patents. This level of carbon monoxide is high for a product intended for human consumption. As a result, the need has arisen to develop a method of reducing the amount of carbon monoxide produced in the combustion of a carbonaceous fuel element.